Power savings in a voltage supply controlled according to a work capability operating mode of an integrated circuit

1. A method comprising: generating a first signal that indicates a state of reduced work capability in an integrated circuit (IC) that is being powered by a switching voltage supply; applying the first signal while the supply is powering the IC in the reduced work capability state, to reduce leakage current through a power switching transistor of the switching voltage supply by turning off a further transistor that (1) is in series with said power switching transistor and (2) has lower leakage current than said power switching transistor; and applying said first signal when deasserted, wherein the first signal when deasserted indicates a state of increased work capability in the IC, to turn on said further transistor while the supply is powering the IC in the increased work capability state.

2. The method of claim 1 wherein the first signal is generated by a processor die.

3. The method of claim 1 wherein the first signal is generated by a system chipset.

4. The method of claim 1 wherein the IC is placed into the state of reduced work capability because one of (1) a thermal overload condition is approaching, (2) a battery is near depletion, and (3) the IC is idle.

5. The method of claim 1 wherein an increase in power efficiency of the switching voltage supply is performed without substantially changing an input supply voltage of the IC.

6. The method of claim 5 wherein said applying the first signal is to further reduce transistor switching loss by reducing switching frequency of a power switching transistor of the switching voltage supply.

7. The method of claim 1 wherein said applying the first signal comprises: changing the switching voltage supply from synchronous operation to asynchronous operation.